The use of electromagnetic measurements in prior art downhole applications, such as logging while drilling (LWD) and wireline logging applications is well known. Such techniques may be utilized to determine a subterranean formation resistivity, which, along with formation porosity measurements, is often used to indicate the presence of hydrocarbons in the formation. Moreover, azimuthally sensitive directional resistivity measurements are commonly employed e.g., in pay-zone steering applications, to provide information upon which steering decisions may be made.
Conventional interpretations of electromagnetic measurements neglect effects from dielectric permittivity, dielectric permittivity anisotropy, dielectric loss factor, permeability, and interfacial polarization phenomena (e.g., in an anisotropic medium). Such conventional interpretations, by their very nature, tend to assume that the electric field in the formation due to an EM source in the borehole is not affected, for example, by the interfacial polarization of clay minerals, clay-sized particles, and conductive minerals.
However, exploration and production in geologically complex reservoirs, such as shaly sands, sand-shale laminations, and organic-rich mudrocks, has become common. Moreover, electromagnetic measurements in these formations may exhibit directional and frequency dispersive characteristics due to the effects of electrical conductivity anisotropy, dielectric permittivity anisotropy, and interfacial polarization phenomena. Therefore, a need remains account for the effects of these parameters when making electromagnetic measurements of geological formations.